RM Italy Amp harmonics to 11th Harmonic at 2 watts input!

[Iceburgh]

Its funny that hardly anyone is using the old school arrl handbook method for settimg up the transciever or amp. First of all the radio's drive should be adjusted so that the peak wattage is four (4) times the level of the dead key. Even if that means turning up or down the radio's drive to get this ratio. Then after the amp is hooked up and turned on, the amps drive should be adjusted to have the same ratio. This is the standard for setting the power vs modulated audio. Using a low pass filter is always a good idea to eliminate certain stray harmonics above the desired frequency. If you turn down the radio to one watt or up to 4 watts, the ratio has to be observed to find the proper operating conditions. You have a million dollars worth of equipment but if the basic fundamentals arent applied then how good is any testing going to be? As long as you have a watt meter that reads peak as well as rms, then the radio and amp can be adjusted properly. Excessive swing or the highest or lowest dead key is not the answer. Proper ratio of both dead key to peak power is. But dont take my word for it. Read it in the ARRL handbook if anyone belives in tested application and sound electronics with proven thechnical theory.

 

[HARDROCK]

Continuing to lower the power does not guarantee an improvement. When you operate equipment below the power output it was designed for you can make matters worse. There's a reason for the low power spec in service manuals.

Very True

Easy-to-Drive Linear Amplifiers
Some hobbyists and manufacturers tout "very low drive" as an advantage, claiming it offers "cleaner signals". Nothing is further from the truth.

Exciters almost always provide the best IM performance when operated at a time-averaged peak power a reasonable amount below full output, rather than very low levels. At low power levels, exciter performance is dominated by cross-over distortion. This is where bias non-linearity or device input threshold induces distortion. The ALC system also adds cutoff bias to early stages. This bias increases distortion in ALC controlled stages. At very high levels, gain compression or negative bias shift becomes an issue. Exciters typically do best when operated in the area of 60-80% of rated power.

Worse yet, low drive amplifiers are especially susceptible to damage from exciter overshoot or transient problems. Transients and overshoot peak power remains almost the same level regardless of exciter power control settings. As exciter operating power levels are reduced, the percent of power overshoot becomes worse.

The most undesirable situations are those where exciter power greatly exceeds (by more than twice) an amplifier's normal drive power limit. Not only does this reduce system IM performance, amplifier drive transients are aggravated. Amplifiers should be designed or selected to match the exciter's maximum power output, or an external attenuator used to bring the amplifier's drive requirement up to the exciter's full power level. Low drive amplifiers are, as a general rule, bad news.

 

[W4KVW]

Well that is a problem. The harmonics end up in the six meter band. If you piss a ham operator off because you just crapped all over a record setting QSO with your harmonics they might not be sympathetic to any trouble you brought to yourself. The six meter band is often referred to as the magic band, 100 watts is considered a big signal.
My first six meter contact I ever made was with only 20 watts and they heard me quite well down in Georgia.

Well 6 meters is my Favorite Band of any were it is legal to talk & if I start hearing CB Signals there they won't need to worry about the FCC stopping it.It will very soon come to a very fast halt.I listen to the CB every day & I would know who the issue is coming from quickly.30 years in State Law Enforcement & being very good friends with the Current Sheriff has big advantages in a lot of ways. {:>)

SIX-SHOOTER

 

[Slowmover]

Very True

Easy-to-Drive Linear Amplifiers
Some hobbyists and manufacturers tout "very low drive" as an advantage, claiming it offers "cleaner signals". Nothing is further from the truth.

Exciters almost always provide the best IM performance when operated at a time-averaged peak power a reasonable amount below full output, rather than very low levels. At low power levels, exciter performance is dominated by cross-over distortion. This is where bias non-linearity or device input threshold induces distortion. The ALC system also adds cutoff bias to early stages. This bias increases distortion in ALC controlled stages. At very high levels, gain compression or negative bias shift becomes an issue. Exciters typically do best when operated in the area of 60-80% of rated power.

Worse yet, low drive amplifiers are especially susceptible to damage from exciter overshoot or transient problems. Transients and overshoot peak power remains almost the same level regardless of exciter power control settings. As exciter operating power levels are reduced, the percent of power overshoot becomes worse.

The most undesirable situations are those where exciter power greatly exceeds (by more than twice) an amplifier's normal drive power limit. Not only does this reduce system IM performance, amplifier drive transients are aggravated. Amplifiers should be designed or selected to match the exciter's maximum power output, or an external attenuator used to bring the amplifier's drive requirement up to the exciter's full power level. Low drive amplifiers are, as a general rule, bad news.

Okay. Noted. Thanks. Will take the Galaxy & RM amp to the McKinney Magician to dial them in a touch better.

Now to Low Pass Filters. The amp spec sheet. states it is so supplied. But let’s say it isn’t.

I’ve gone on line to look for a LPF. The name BENCHER comes up and it is discontinued at DX & Universal. (Another, older name which escapes me, in other threads). Only used ones at EBay & eHam & QRZ. (Don’t know the vagaries of used in this).

Assuming a good one found, it would be

Radio — LPF — Amp (correct?)

And if a quality 11-meter bandpass filter can built:

Radio — LPF — Amp — BF (?)

(The coax has gotten busy as already have a PALOMAR CMC Filter between the amp and the tuner. From there to the antenna feedpoint is another type PALOMAR feedpoint choke. Thus:

Radio — CMC filter — LPF — Amp — BF — Tuner — Feed Choke — Antenna.

Saying today’s big trucks are noisy is an understatement. As my pickup and travel trailer (the “real” base station) will also need optimum installs, it’s some fun to try out gear in the big truck.

1). Get radio/amp at 4:1 each
2). Low Pass Filter
3). Bandpass Filter

Given what I’ve read at this site this may not have the effect of cutting spurious emissions. But is it not a start?

I wish to cut noise, but also not create any. It’s a while later 2019 till a better mobile radio, gentlemen.

.

 

[kopcicle]

Erm , No.
Radio > Amplifier > LPF
Look for "Drake" , "Nye-Viking" , "B & W" (Barker and Williamson)
In my case it's Radio > BPF > Amplifier > LPF .

Note: most modern multiband radios have a fairly robust BPF . Very few can benefit from an additional/external BPF. One instance I can think of is trapping MW broadcast and harmonics.
Another is multi/multi contest stations where 80m can be divided up as many as 4 ways and the filters provide significant attenuation for the other portions of the band.

I'm not using a resonant antenna in the classic sense. It "hears" everything. Additional pre-select/band pass was purely self defense. I'm deep in the urban RFI cesspool . The LPF is just me attempting to stay out of my neighbors toaster and other services. Reasoning was I eliminated the complexity of switching the BPF in and out and maintained the intended preselect pass band for the receiver while delivering a bit less "noise" to the Amplifier.
In any case the LPF should be the last thing in line . This includes your watt meter. I have seen the diode pick up in a watt meter produce significant noise that the LPF will, to some degree remove.

 

[Slowmover]

Thank you, sir.

I’ve found an online source selling a wide variety of used Low Pass Filter brands, NATIONWIDE RADIO.

Now, although the amp has such built-in, can anyone think of a reason it might be a good idea in a big truck mobile installation?

If I’m keying 180w, I’m not at all disposed to creating problems.

I realize truck familiarity may factor, so think of your personal vehicle, and then upsize your order to GIGANTO SUPER SERVING.

I have a thread: “Mobile Install: 579 Peterbilt” currently running where your thoughts on the subject of interference creation would be appreciated.

Thx.

.

 

[Tallman]

Worse yet, low drive amplifiers are especially susceptible to damage from exciter overshoot or transient problems. Transients and overshoot peak power remains almost the same level regardless of exciter power control settings. As exciter operating power levels are reduced, the percent of power overshoot becomes worse.

The most undesirable situations are those where exciter power greatly exceeds (by more than twice) an amplifier's normal drive power limit. Not only does this reduce system IM performance, amplifier drive transients are aggravated. Amplifiers should be designed or selected to match the exciter's maximum power output, or an external attenuator used to bring the amplifier's drive requirement up to the exciter's full power level. Low drive amplifiers are, as a general rule, bad news.

Matching your gear is just as important as matching your antenna impedance.
I don't use amps but I do collect them. I have amps that were made for cb and will work on 10 meters, but my 10 meter radios would smoke any of those amps and only bump my signal one S unit on the receive end. My ham radios put out 100 watts dead key so any more output power would be unnecessary. Unless I go way down in frequency.
40 meter down to 160 meter takes power to get very far.